Just need t plug in anything in these GFCI's to check them. Since these washlets are always powered just for the electronics, when plugging in they will immediately trip. A GFCI wired with the load and line side flipped, the GFCI will not power up at all.
I think this is a new installation for these seats and someone wired in two GFCI's incorrectly by using a common neutral. For 1.4KW max this would require two separate circuits and maybe one 12-3 was run, however, any licensed electrician would know this, so who installed these GFCI's?